sea letter

plural sea letters · alternative sea-letter

1. historicalnauticalA certificate issued by a neutral country, usually at a custom house, to a merchant ship and its crew, cargo etc. during wartime, allowing them to pass safely through waters of a belligerent. Often synonymous with the term "passport".

   […]where such ship or vessel is in possession of a sea letter, or other regular document, issued from a custom-house of the United States, proving such ship or vessel to be American property.

   1805, United States Congress, An Act to amend an act intituled “An act for imposing more specific duties on the importation of certain articles, and also for levying and collecting light money on foreign ships or vessels, and for other purposes"

   Synonyms: sea brief, sea pass